Municipal wastewater treatment plants use activated sludge process to treat waste water, producing large amounts of sludge. China's annual discharge of dewatered sludge is close to 22 million tons. The activated sludge at room temperature is difficult to dry out, and therefore cannot be used directly. Bacterial cell walls are usually resistant to damage unless heated to a temperature higher than 298° C. But the drying process is very energy consuming.
At present, common methods for treating activated sludge include using activated sludge as composts to produce fertilizer, drying activated sludge to be used for landfills, press drying and incineration, and using activated sludge to produce ceramic filter tiles. However, there are issues in these treatments, e.g., heavy metal precipitation and pathogens and virus contamination in the fertilizer used for composting, pollution of groundwater by the landfills, and production of waste gas and dioxins and high energy consumption in filter press drying. To produce ceramic filter titles, there is a need to include additional amount of clay, and the production is costly and inefficient in energy consumption.
This invention relates to a biochemical ceramic, whose production method and application has been disclosed in Chinese Patent Application No. 200810238351.0, filed on Dec. 15, 2008. The biochemical ceramics is calcined under anoxic condition using waste water sludge-based material, with calcium carbonate or gypsum, clay, calcium hydroxide dihydrate, liquid wax, iron powder or iron oxide powder and other materials. The biochemical ceramics need to be calcined at a temperature of 1000° C. or greater so the bacteria in the sludge can be completely burned and no template or mesopores will be formed. Thus the biochemical ceramic has no mesopores but only micropores. The biochemical ceramics can be used in water treatment to remove TCOD, ammonia, ammonia nitrogen and hydrogen sulfide in water bodies, and can also be used as biological media for bacterial screening. However, the biochemical ceramics requires a high calcination temperature which leads to large energy consumption and high cost.